The proposed studies will utilize a recently-developed NH3 gas electrode for further elucidation of the relation of ammonia to the syndrome of hepatic encephalopathy: (1) The relation of arterial and venous plasma ammonia to degree of cerebral dysfunction. (2) The relation of colonic gas NH3 to stool NH3 and total ammonia, and to peripheral plasma ammonia. (3) The pK'a of ammonia in plasma and feces. (4) The relation of cerebro spinal fluid ammonia to plasma ammonia and existing pH gradients, according to non-ionic diffusion theory. (5) Release and kinetics of artifactual NH3 from plasma and other protein solutions, peptides and amino acids. (6) Ammonia absorption from the intestine.